School of Information, Kochi University of Technology, Kami 782-8502, Kochi, Japan.
School of Computer Science and Information, Hefei University of Technology, Hefei 230601, China.
Sensors (Basel). 2023 Mar 9;23(6):2981. doi: 10.3390/s23062981.
The optical filter is critical in many applications requiring wide-angle imaging perception. However, the transmission curve of the typical optical filter will change at an oblique incident angle due to the optical path of the incident light change. In this study, we propose a wide-angular tolerance optical filter design method based on the transfer matrix method and automatic differentiation. A novel optical merit function is proposed for simultaneous optimization at normal and oblique incidents. The simulation results demonstrate that such a wide-angular tolerance design can realize a similar transmittance curve at an oblique incident angle compared to a normal incident angle. Furthermore, how much improvement in a wide-angular optical filter design for oblique incident contributes to image segmentation remains unclear. Therefore, we evaluate several transmittance curves along with the U-Net structure for green pepper segmentation. Although our proposed method is not perfectly equal to the target design, it can achieve an average 50% smaller mean absolute error (MAE) than the original design at 20∘ oblique incident angle. In addition, the green pepper segmentation results show that wide-angular tolerance optical filter design improves the segmentation of the near-color object about 0.3% at 20∘ oblique incident angle compared to the previous design.
光学滤波器在许多需要宽角成像感知的应用中至关重要。然而，由于入射光的光路变化，典型的光学滤波器的传输曲线会在斜入射角度发生变化。在这项研究中，我们提出了一种基于传递矩阵法和自动微分的宽角容差光学滤波器设计方法。提出了一种新的光学优值函数，用于同时优化正常和斜入射。模拟结果表明，这种宽角容差设计可以在斜入射角度实现与正常入射角度相似的透过率曲线。此外，对于斜入射的宽角光学滤波器设计，其对图像分割的改进程度尚不清楚。因此，我们使用 U-Net 结构评估了几种透过率曲线在青椒分割中的应用。虽然我们提出的方法并不完全等同于目标设计，但与原始设计相比，在 20∘斜入射角度下可以平均减少 50%的平均绝对误差（MAE）。此外，青椒分割结果表明，与之前的设计相比，在 20∘斜入射角度下，宽角容差光学滤波器设计可以将近色物体的分割提高约 0.3%。
